Fail safe device

ABSTRACT

A housing having a chamber has an inlet and an outlet for directing therethrough a fluid under pressure to an associated fluid pressure responsive apparatus; a filter situated generally in the path of flow of such fluid becomes effective after it experiences a degree of clogging by dirt to open an additional outlet as to thereby enable such fluid under pressure to be directed to the fluid pressure responsive apparatus through such additional outlet.

RELATED APPLICATION

This application is a division of my co-pending application, Ser. No.355,819 filed on Apr. 30, 1973.

BACKGROUND OF THE INVENTION

In many situations in the prior art, as in for example, turbine enginefuel controls, a gauged or sensed flow through fluid pressure isemployed for in turn conveying a signal pressure to related apparatuswhich appropriately respond thereto. That is, some circumstances, againwith respect to turbine engine fuel control systems for example, anengine operating parameter may be sensed in the form of a variablemagnitude fluid pressure which varies to be indicative of such operatingparameter. Such fluid pressure may, in turn, be directed to associatedapparatus which, for example, may respond thereto in a manner whereby areduction in the magnitude of the fluid pressure sensed by suchassociated apparatus causes such associated apparatus to react bydictating that an increased rate of fuel flow should be delivered to theengine.

Quite often in such systems employing pressurized fluid flow, suitablefilter means must be provided as to continuously filter dirt and foreignparticles from the flowing pressurized fluid. Where such filter meansare provided, for example, upstream of the said associated apparatus,problems have occurred because as the filter becomes progressivelyclogged with filtered dirt, the filter creates an increasing pressuredrop thereacross with the result that the said associated apparatussenses what it believes to be an actual reduction in the magnitude ofthe pressurized fluid caused by a change in the engine operatingparameter and consequently results in a greater rate of fuel flow to theengine whereas, in reality, the actual reduction in magnitude ofpressurized fluid was due solely to the filter becoming clogged withdirt. In such situations, the erroneously increased rate of fuel flowmay well be damaging to the engine.

Accordingly, the invention as herein disclosed and described isprimarily directed to the solution of the above as well as other relatedproblems.

SUMMARY OF THE INVENTION

According to the invention, a fail safe device has a housing definingchamber means, an inlet for admitting a relatively high pressure fluidthereto, a first outlet for directing said fluid from said chamber meansto associated means for action upon said associated means in response tothe magnitude of said fluid pressure, and filter means situatedgenerally in the path of flow of said fluid, second outlet means for attimes directing said fluid pressure to said associated means, andvalving means for controlling the communication between said secondoutlet means and said chamber means, said valving means beingoperatively controlled by the deflection experienced by said filtermeans due to a pressure differential thereacross generated by said fluidpressure due to an increasing restrictive effect to flow through saidfilter means created by clogging of said filter means as by particles ofdirt.

Various specific and general objects and advantages of the inventionwill become apparent when reference is made to the following detaileddescription considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein for purposes of clarity certain details andelements may be omitted from one or more views:

FIGS. 1, 2 and 3 are views each illustrating a portion of a fuel controlconstructed in accordance with the teachings of the invention which,when combined as indicated, illustrate the preferred embodiment of theturbine engine fuel control of the invention;

FIG. 4 is a graph illustrating engine curves of the invention obtainedby plotting, generally, a function of engine compressor dischargepressure against a function of air flow;

FIG. 5 is a graph illustrating operating curves obtained by plottingfuel flow to the engine against compressor discharge pressure;

FIG. 6 is a graph illustrating, generally, operating curves and regionsobtained by plotting fuel flow to the engine against engine speed; and

FIG. 7 is a schematic logic diagram illustrating in greater detail oneof the elements shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in greater detail to the drawings, FIGS. 1, 2 and 3collectively illustrate a preferred embodiment of a fuel control system10 employed for controlling the rate of metered fuel flow to anassociated turbine engine 12 as well as controlling the load of suchengine.

Suitable pumping means 14 provided, as in FIG. 3, functions to take fuelout of the related source of fuel 16 and supply such fuel to an inlet 18of the fuel control 10 wherein suitable filter means such as a screen 20is provided. The pumping means 14 may be provided with a pressure reliefbypass valve 22; however, since any suitable pumping means may beemployed, if pumping means 14 should be a centrifugal pump, no suchbypass return system need be provided.

An inlet pressure regulator assembly 24 is illustrated as beingcomprised of housing portions 26 and 28 which cooperate with each otheras to peripherally contain therebetween a pressure responsive diaphragm30 and thereby define an opposite sides thereof chambers 32 and 34 withchamber 34 being vented as at 36 to the ambient atmosphere while chamber32 is suitably placed in communication with a chamber 38, formed withinhousing portion 26, as by passage means 40. Throttling type valvingmeans comprised as of a valve portion 42 and valve stem 44, suitablysecured to the diaphragm 30, effectively determines separation ofchamber 38 and a second chamber 46 within housing portion 26, as bycooperation of the valve portion 42 with a coacting annular valve seat48. A spring 50 generally situated within chamber 34 normally urgesdiaphragm 30 and valving means 41 toward the left and in the openingdirection.

A fuel pump assembly 52 is shown as being of the gear-type having gearsor rotors 54 and 56 within a housing 58 so as to have an inlet 60thereof in communication with chamber 46 of regulator 24 as via conduitmeans 62. Rotor 56 is suitably drivingly engaged to a shaft 64 which, aswill later be discussed, is operatively connected to the engine 12. Anoutlet 66 of pump assembly 52 is placed in communication with relatedspeed sensing means 70 (FIG. 2) as by conduit means 68.

The speed sensing means 70 may be comprised of housing means 72 definingtherein a chamber 74 in which is situated a rotor 76 drivingly engagedto suitable motion transmitting means responsive to the speed of engine12. Such motion transmitting means, as shown, may take the form of shaftmeans 78 operatively drivingly engaged to shaft 64 and, at its upperend, to rotor 76.

A first radially directed passage 80 formed in rotor 76 intersects andcommunicates with a centrally disposed axially aligned passage 82. Asecond somewhat radially disposed passage 84 communicates as betweenchamber 74 and passage 80. The degree to which communication ispermitted between passage 80 and axial passage 82 is dependent upon theposition of valving means 86 and valve portion 88 thereof.

A cup-like seal 90, urged into sealing engagement with rotor 76 as by aspring 92, has an aperture 94 formed therein as to permit continuouscommunication of passage 82 with branch conduit means 96. Conduit means98, formed in housing 72, communicates with conduit means 68 and withchamber 74 as by conduit portion 100 and calibrated restriction means102.

A muscles valve assembly 104 comprised of a housing portion 106 has achamber 108 formed therein which is in continuous communication withbranch conduit means 110. An inlet 112, communicating with conduit means98 as via interconnecting conduit means 114, is in controlledcommunication with chamber 108 by the action of a generally cylindricalvalve 116 resiliently urged toward the closing direction as by a spring118.

Branch conduit 96 communicates with conduit 110 which leads to conduitmeans 120 having one end in communication with the inlet 122 of a reliefvalve assembly 124 which may be comprised of housing means 126 having achamber 128 formed therein and containing spring means 130 which servesto urge a relief valve 132 toward its illustrated closed position. Whenit occurs that valve 132 is suffiently moved to the right, generallyradially formed ports 134 complete communication between chamber 128 anda medially disposed axially extending passage 136 which is incommunication with inlet conduit portion 122. A conduit 138 serves tocomplete communication as between chamber 128 of relief valve assembly124 and chamber 46 of the inlet pressure regulator assembly 24 (FIG. 3)while a second conduit 140, also in communication with chamber 128,leads to a metering pressure head regulator assembly 142 shown in FIG.2.

The regulator assembly 142 is illustrated as comprising housing meansincluding housing sections 144, 146 and 148 with housing sections 144and 146 cooperating to peripherally retain therebetween a pressureresponsive diaphragm 150 so as to thereby define chambers 152 and 154 onopposite sides thereof, while housing sections 146 and 148 cooperate toperipherally retain therebetween a second pressure responsive diaphragm156 so as to thereby define chambers 158 and 160 on opposite sidesthereof.

A sleeve-like member 162, provided with a plurality of radially directedports 164, is suitably fixedly secured within housing section 144 in amanner so as to have the inner passage 166 of sleeve 162 incommunication with conduit 120 while ports 164 are in communication withan annular chamber 168 formed within housing section 144. As can beseen, conduit means 120 also communicates directly with chamber 152.

A generally tubular axially movable valving member 170 is slideablyreceived within sleeve 162. When, as will become evident, valve member170 is sufficiently moved to the right, the end 174 thereof will uncoverports 164 of sleeve 162 and permit such ports to complete communicationbetween conduit 120 and conduit 140 leading to the relief valve assembly124.

As can be seen, the right end of valve 170 is fixedly secured to, as byopposed diaphragm plates, to diaphragm 150 and is urged toward the rightby resilient means in the form of a spring 176 situated generally withinchamber 152.

Motion or force transmitting means in the form of a rod 178 sealinglyslideably received through a wall of housing section 146 operativelyabutingly engages, at one end, valve member 170 and, at an other end, amember 180 operatively secured to and carried by diaphragm 156. A spring182, situated against an adjustable spring seat 184, is containedgenerally within chamber 160 and urges diaphragm 156 to the left.

Chamber 160 connumicates with one end of conduit means 186 leading tomeans generally sensitive to engine compressor discharge pressure;chamber 158 is vented to the ambient atmosphere via conduit or portmeans 188; and chamber 154 communicates via conduit means 190 withconduit means 192 downstream of variable restriction means comprising aportion of an assembly 194 generally sensitive and responsive to theinlet temperature of the engine burner.

Assembly 194 is shown as being comprised of housing means 196 having achamber 198 with a valve orifice plate 200 held against one wall thereofas to define an orifice 201 for communicating between chamber 198 and asecond passage or chamber 192. An axially adjustable and slideable valvemember 202 having a valving surface 203 is threadably secured to anaxially slideable rod 204 the other end of which is secured to athermally responsive member 207 which, in turn, is secured via member205 to a second thermally responsive member 206. The rates of expansionof members 206 and 207 are different from each other and are such as tocause valving surface 203 to more nearly close orifice 201 as the burnerinlet temperature increases. Thermal elements 206 and 207 are, ofcourse, placed as to be exposed to the air at the inlet of burner 214 asto respond thereto. A suitable perforated protective shroud 208 may beprovided about such thermal elements 206 and 207.

As indicated, a spring 209 normally urges rod 204 and valving member 202in a direction tending to reduce the effective flow area of orifice 201,while a second spring 210 resiliently holds a minimum pressurepressurizing valve 211 seated as to force the initial fuel flow to passthrough the calibrated restriction passage 213 while, when normal fuelflow to the engine is attained, permitting valve 211 to move to the leftand thereby opening additional passages 215 for the flow of fueltherethrough.

Referring to both FIGS. 1 and 2, it can be seen that conduit means 110communicates with a vertically depicted conduit means 234 the upper endof which is shown in FIG. 1 communicating with an inlet 236 of a housingsection 238 of a main metering valve assembly 240.

The main metering valve assembly 240, as shown in FIG. 1, is illustratedas being comprised of housing means including housing sections 238 and242 which cooperate to peripherally retain therebetween a pressureresponsive diaphragm 244 which, in turn, is suitably fixedly secured toa valving member 246, slideably received and positioned within acylindrical guide portion 248, and defines chambers 250 and 252. Chamber252, of course, communicates with inlet 236 as well as a metering outletorifice 254, while chamber 250 communicates with chamber 74 of the speedsense means 70 (FIG. 2) as via conduit means 256 and 258. Restrictionmeans 260 is preferably provided as a damping means.

Orifice 254, which communicates with an inlet 255 of assembly 194 asthrough an outlet 262 and conduit means 264, cooperates with end 266 ofthe variably positionable metering valve 246 to determine a firsteffective metering orifice area. That is, the more valve member 246moves to the right, the more nearly the effective flow area throughorifice 254 is reduced. An axially positionable abutment member 268provides a stop against which the end 266 of valve 246 may at times abutthereby enabling the manual adjustment of the maximum degree to whichthe flow area through orifice 254 may be reduced and consequentlyestablish an assured minimum flow therethrough.

A rotatable shaft 270, journalled in housing section 238, has a cam 272fixedly secured thereto for rotation therewith. The cam 272 is adaptedfor engagement with a cam-follower portion 274 of a lever 276 which hasone end pivotally anchored, as to a pin 278 carried by the housingsection 238, and an other end 280 of a fork-like or yoke-likeconfiguration extending generally about the exterior of the cylindricalguide 248.

The forked end 280 of lever 276 abuts against the end of a collar-likespring seat 282 which serves to contain a spring 284 between itself andthe diaphragm cup 286 of diaphragm 244. Generally, as shaft 270 and cam272 are rotated in a direction cuasing lever end 284 to swing generallyto the left, spring seat 282 moves spring 284 and, through diaphragmplate 286, metering valve 246 to the left until such time as manuallyadjustable abutment 288 is engaged after which any further movement oflever fork portion 280 and spring seat 282 results in the compression ofspring 284 thereby creating an increased pre-load in the spring 284. Anadditional manually axially adjustable abutment member 290 may be set asto thereby provide a stop against which lever 276 may act in order tothereby establish a minimum rate of fuel flow through the orifice 254during conditions of idle engine operation.

As also shown in FIG. 1, shaft 270 has a lever 292 suitably securedthereto for free rotation relative thereto. Lever 292 is provided with afirst arm portion 294 which through linkage means 296, 298 and bellcrankmeans 300 is operatively connected as to a vehicle operator's footcontrolled pedal or lever 302 pivotally mounted as at 304. A second armportion 306 has a pin member 308 secured thereto and passingtherethrough as to extend into a slot 310 formed in a second lever 313which is suitably fixedly secured to shaft 270 for rotation therewith.In addition to pin 308 and slot 310 levers 292 and 313 are operativelyinterconnected as by a spring 314. A fixed pivot 316 pivotally supportsa lever 318 having one end provided with an adjustable abutment 320adapted to at times operatively engage and position a related enginepriority valve member 312. The other end of lever 318 constitutes a camfollower which operatively engages suitably contoured cam surfaces 321and 322 provided or carried as by angularly adjustably positionablemeans 291 and 293 secured to lever 292. A main return spring 324 havingone end operatively connected to lever means 292 as by being engagedwith pin 308, has its other end anchored to related fixed anchor means326. Further, adjustably positionable fixed stops or abutments 328 and330 are adapted to provide for abutting engagement with lever armportion 329 of lever 313 to thereby respectively determine what may bereferred to as a maximum engine speed position and an idle engineoperating condition.

Referring now to FIG. 3, a vehicular transmission assembly 332 having aninput shaft 334 and an output shaft 336 is shown provided with suitablecontrol means 338 operatively connected as by conduit means 340 to atransmission actuator valve assembly 342 (FIG. 2) which is operativelycoupled to a related control means 344. The output shaft 336 is showncoupled to, for example, the ground-engaging drive wheels 346 of arelated vehicle.

The transmission 332 is preferably of the type which has the ability, asis well known in the art, to provide variable speed and torquetherethrough. One such type of transmission employs a fluid-typecoupling in the drive train with, for example, variably positionableguide vanes in the fluid coupling for varying the torque transmittedtherethrough. For pusposes of discussion, it will be assumed thattransmission 332 is so provided with a fluid coupling in which guidevanes are variably and adjustably positionable and that control means338 is effective for causing such variable adjustment of the guidevanes.

Referring to FIG. 2, it can be seen that control means 344, among otherthings, comprises assemblies 348, 350 and 352.

Referring to such in greater detail, it can be seen that assembly 348comprises housing sections 354, 356 and 358 with sections 354 and 356generally containing therebetween a screen member 360 with such screenpermitting substantially unrestricted flow from one side thereof or area362 to the other side thereof or area 364. Suitable sealing means, notshown but well known in the art, may be provided as to prevent anyleakage out of such areas 362 and 364 generally between housing sections354 and 356 and screen 360. As will become apparent, screen 360 doeshave the capability of undergoing deflection. A valving member 366,suitably secured to screen 360 is urged into sealing engagement with aportion of housing section 354, as by spring means 368, in order tothereby prevent communication as between chamber-like area 362 and anotherwise open end of a conduit 370. An inlet 372, formed in housingsection 354, communicates with a source 226 of compressor dischargepressure as via conduit means 374.

Housing sections 356 and 358 also combine to peripherally retain apressure responsive diaphragm 376 therebetween as to define chambers 378and 380 at opposite sides thereof with chamber 378 communicating as viapassage 382 with conduit means 384 leading from chamber-like area 364while chamber 380 communicates with the ambient atmosphere as by conduitmeans 386, 388 and 390. A spring 392 normally urges diaphragm 376 and avalving member 394, suitably secured thereto and having valving portions396 and 398, to the left. As can be seen, valving member 394 extendsthrough sized passage means 400 which communicates generally betweenconduit 384 and a conduit 402 having a calibrated restriction 404therein. As indicated, suitable adjustable stop members 406 and 408 maybe provided.

Assembly 350 is illustrated as comprising housing sections 410 and 412which cooperatively peripherally retain therebetween a pressureresponsive diaphragm member 414 as to define at opposite sides thereofchambers 416 and 418 with chamber 416 communicating with conduits 420and 402 as by conduit means 422. A valving member 424, slideablyreceived in housing section 410, has an upper valving portion 426adpated for controlling communication as between a passage 428 and achamber 430 while the lower disposed body portion 432 is operativelyconnected to a moveable spring seat 434 resiliently urged, as by aspring 436, into operative abutting engagement with a diaphragm plate438 carried by diaphragm 414. A spring 440 situated in chamber 418 urgesthe diaphragm 414 and plate 438 upwardly into such operative abuttingengagement with valve member 424. A suitable adjustable spring seat maybe provided as at 442 while an adjustable stop or abutment member may beprovided as at 444. As can be seen, chamber 430 communicates withconduit means 390, which contains calibrated restriction means 446;passage 428 communicates with chamber-like area 364 of assembly 348 viaconduit means 448; while chamber 418 communicates with conduit means 450leading to assembly 352.

Assembly 352 is illustrated as comprising housing sections 452, 454, and456 with sections 452 and 454 combining to peripherally retaintherebetween a pressure responsive diaphragm 458 which is operativelyconnected, via an intermediate member 460, to a second diaphragm 462which is peripherally retained by housing sections 454 and 456. In suchan arrangement, chambers 464, 466 and 468 are defined at opposite sidesof such diaphragms 458 and 462.

As spring 470 urges diaphragms 458 and 462 along with a valving member472 toward seated engagement with a variably adjustable valve seatmember 474 having a passage 476 formed therethrough and communicatingwith conduit means 478 leading to a relatively low pressure hydraulicreservoir or sump 480. Chamber 468, aside from communicating withchamber 418 via conduit means 450, also communicates with conduit means482 leading to the transmission control valve assembly 342. Chamber 464communicates, as by conduit means 484 with a source 486 of total airpressure at the inlet of the engine 12, while intermediate chamber 466communicates with a source 488 of static air pressure at the inlet ofthe engine 12 as by conduit means 490.

Transmission control valve assembly 342 is illustrated as comprisinghousing sections 492 and 494 cooperating to peripherally retain apressure responsive diaphragm 496 therebetween so as to define chambers498 and 500 on opposite sides thereof. A spring 502, operativelyengaging a diaphragm plate 504 of diaphragm 496, resiliently urges thediaphragm 496 downwardly against a spooltype valve member 506 slideablyreceived within a sleeve valve guide 508 fixedly secured within housingsection 494. A lower disposed spring 510 urges the valving member 506upwardly against diaphragm 496.

A plurality of radially directed ports 512, formed in sleeve 508, serveto complete communication as between the passage 514 slideablycontaining valving member 506 and conduit means 516 leading to conduitmeans 478 and low pressure sump. A second plurality of ports 518 serveto complete communication as between a portion of passage 514 andconduit means 520 leading to pumping means 522 for supplying arelatively high substantially constant hydraulic pressure. A thirdplurality of ports 524 are controlled by valve portion 526 of valvingmember 506 as to selectively complete communication between either therelatively low or relatively high hydraulic pressure within passage 514and conduit means 340 leading to the transmission control means 338(FIG. 3).

As can be seen, the inlet conduit 520 also communicates with conduitmeans 482 as by a conduit 528 including calibrated restriction means530. An adjustable spring seat may be provided as at 532, and chamber498, generally containing spring 502, communicates via conduit means 534with conduit 402 as at a point upstream of restriction means 404. Asshown at 536, conduit means 370 is also placed in communication withconduit 534.

The transmission priority valve assembly 538 (FIG. 1) is shown as beingcomprised of housing means 540 having a chamber 542 formed therein whichopenly communicates with one end of conduit 388 and also restrictivelycommunicates with conduit 420 as by means of a contoured valving portion546 of valve member 312 coacting with an orifice 548. Spring means 550situated as within chamber 542 urges valve member 312 upwardly and awayfrom the cooperating orifice 548.

FIG. 1 also illustrates a compressor inlet air temperature sensorassembly 552 (also diagrammatically depicted at 552a within theschematically illustrated engine assembly 12) which may be comprised ofbody or housing sections 554 and 556 combining to define a chamber 558which is vented to the atmosphere as at 560 and in communication withconduit 420 via conduit means 562 and orifice 564. A valve guideportion, about which is located a spring 566, slideably contains theshank of a valve member 568 having a valving portion 570 adapted tocoact with orifice 564. The other end of valve member 568 hasoperatively secured thereto, as by a screw 572, a plurality of stackeddish-like thermostatic members 574, 576, 578 and 580 which, depending onthe temperature experienced will either become more flattened or moredished and, consequently, by reacting against a portion of housing 556,cause valve member 568 to respectively move closer to or further awayfrom orifice 564 thereby increasing or decreasing the restrictive effectto flow through orifice 564. A suitably perforated cuplike guard 582 maybe provided to protect the thermostatic means.

In the preferred embodiment a solenoid operated over temperatureresponsive valve assembly 584 (FIG. 2) is preferably provided as to havepassage means 586, formed within housing 588, in communication withconduits 562 and 420. A solenoid assembly 590 controls the position of avalving member 592 carried thereby so as to at times either terminate orcomplete communication as between passage 586 and a chamber 594 viacalibrated orifice 596. An electrical conductor 598, for actuating thesolenoid 590, is operatively connected to suitable related startsequence logic means 600 (FIG. 3).

Also, as shown in FIG. 1, pressure responsive switching means 602 arepreferably provided and, as illustrated, may be comprised ofelectrically non-conductive housing means 604 and 606 which cooperate toperipherally retain therebetween a pressure responsive wall member 608which, for ease of illustration and description, may be described asbeing electrically conductive. A chamber 610 formed on one side of wall608 communicates as between conduit means 256 and 258 while chamber 612,on the other side of wall 608, communicates with conduit means 234 as byconduit means 614.

Adjustably positionable fixed contact type terminals 616 and 618,provided and placed in general juxtaposed relationship to a moveablecontact 620 carried by the wall member 608, are respectivelyelectrically connected as via conductor means 622 and 624 to the controlmeans 600. An electrically conductive spring 626 situated generally inchamber 612 and in conductive engagement with wall 608 is also inelectrically conductive engagement with a portion of a third terminal628 which, in turn, is electrically connected as via 630 to the control600. Spring 626, of course, normally biases moveable wall 608 towardchamber 610 and the contact of terminal 616 which biasing may begenerally modified or offset as by a second spring within chamber 610.

Referring now to the remaining portions of the schematically representedengine 12, it can be seen that it is of the solid shaft type wherein thecompressor turbine and power turbine is one and the same turbine wheel632 connected by solid shafting means 634 to the compressor 636 so thatthere is no degree of free relative rotation therebeteen. Suitable gearbox means 638 may be employed for providing speed motion transmittingmeans 640 to the shaft 64 of FIG. 3.

Generally, air flow through the engine is depicted by the lines witharrows provided thereon to indicate generally that the air entering thecompressor is discharged passing through compressor discharge sensingmeans 226 and a heat exchanger or regenerator 642 and then, through anarea 644 for receiving the heat sensing portion of assembly 194, to thecombustion chamber or burner 214 from where the hot expanding gases passthrough stator means 646 and the turbine wheel 632 thereby driving thewheel 632 as well as the compressor 636. In the main, the remaining workis transmitted as via shaft 634 to the input shaft 334 of transmissionassembly 332 (FIG. 3). Instead of exhausting the gases directly toatmosphere, such are directed to the hot side of the regeneraor 642 tothereby recover heat energy and supply such recovered heat to the airpassing through the cold side of the regenerator. After such hot gasescomplete their passage through the regenerator they are exhausted to theatmosphere as by suitable conduit means 646 formed in housing 648. Asshown, the burner 214 may be interconnected to the metered fuel outlet650 as by conduit means 652 and serially situated cooperating valvemeans 654 which may comprise a master electrically operated shutdownvalve.

OPERATION OF INVENTION

Fuel at a pressure P₁ is supplied by pump means 14 (FIG. 3) to chamber38 from where the pressure is also applied to chamber 32 and diaphragm30. The fuel passing around throttling valve 41 is reduced in pressureto a value of P₂ which, in turn, is communicated to the inlet of pump 52and to chamber 128 of valve assembly 124 as well as to chamber 168 ofmetering pressure head regulator assembly 142 (FIG. 2).

The rotation of pump assembly 52 (FIG. 3) in turn causes the fuel to beincreased to a pressure P₃ as within passage means 98 and, upon passingthrough muscles valve assembly 104 subsequently is reduced to a pressureP₄ as within conduit means 110, 96, 120 and 234. Conduit 234 leads tothe governor valve assembly 240 (FIG. 1) while conduit 120 communicatesbetween inlet 122 of relief valve assembly 124 and the metering headregulator 142 (FIG. 2). As is apparent, whenever pressure P₄ shouldexceed a maximum value, valving member 132 of relief valve assembly 124is moved to the right against spring 130 thereby venting or bleeding,via 134, such excess pressure to the low pressure P₂ of chamber 128 andconduit 138.

The value of pressure P₅ within speed sense means 70 is a valuegenerally dependent on the speed of rotation of rotor 76 and, as itslimits, it would have the value of pressure P₃ at its upper magnitudelimit and pressure P₄ on its lower magnitude limit. That is, rotation ofrotor 76 causes, by centrifugal force, valve 86 to tend to move radiallyoutwardly and such tendency to move outwardly is overcome or resisted bythe value of the pressure of fuel within chamber 74. As will becomeapparent, valve 86, during transient operating conditions of increasingpower demands, will remain generally in the position illustratedeffectively terminating communication through conduit 84 as betweenchamber 74 and passage 82 until the speed of pump means 52 has increasedsufficiently to cause pressure P₃ to increase to a new value which willresult in valve 86 being moved radially inwardly.

Assuming the engine is operating at a steady state condition, some flowwill be occurring from chamber 74 through passage 84 and into passage 82thereby resulting in a stabilized pressure differential of P₅ - P₄ whichis applied across diaphragm 244 of governor vlave assembly 240 (FIG. 1).Such pressure differential is suficient ot maintain metering valve 246in a particular relationship with respect to orifice 254 therebypermitting a particular rate of flow of fuel therethrough dependent onthe pressure differential of P₄ - P₆ thereacross. Depending on thetemperature of the engine burner inlet variable restriction meansdefined by orifice 201 and valve portion 203 will cause the fuel toexperience a pressure drop of P₆ - P₇ thereacross and such pressure P₇is communicated to chamber 154 of metering head regulator 142 (FIG. 2)where it acts against diaphragm 150 which has its other side exposed topressure P₄. Accordingly, it can be seen that the actual metering isdetermined by an effective metering orifice size, which is comprised ofmetering orifice 254, of governor valve assembly 240, and variablyrestricted orifice 201 of temperature compensator 194, and a pressuredifferential which is actually determined by P₄ - P₇. Without at thistime considering the effect of the compressor discharge pressure on theoverall system, it can be seen that generally valve 174 of the meteringhead regulator assembly 142 (FIG. 2) will, by axial movement, causeports 164 to be opened and/or closed in order to thereby modulate thevalue of pressure P₄ so as to thereby maintain a desired value ofpressure differential P₄ - P₇.

As can be seen in both FIGS. 1 and 2, compressor discharge pressure(CDP) at a magnitude P_(t1) sensed as at 226 of engine 12 is suppliedvia conduit means 374 to assembly 344 (FIG. 2). As such air pressureflows through passage 428, regulated by valve 426, of assembly 350, apressure drop is realized, due to the flow permitted by calibratedrestriction means 446, resulting in a modified pressure signal of P_(t4)being transmitted via conduit means 390 and 186 to chamber 160 ofmetering head regulator 142 (FIG. 2). Therefore, it should be apparentthat as the value of magnitude of P_(t4) increases diaphragm 156 throughforce transmitting means 178 will exert an increased force against valvemember 174 so as to at least tend to prevent communication as betweenpassage 120 and conduit means 140 through ports 164. In the main, P_(t4)will experience such increases in magnitude during increases in enginespeed as may occur in consequence to requests for increase in enginepower.

If the engine is operating at a steady state condition and an increasein power is desired or required, the pedal or power lever 302 is rotatedcausing levers 292 and 313 along with shaft 270 to rotate generallyclockwise with the result that cam 272 urges lever 276 to move springseat 282 to the left causing the governor valve 246 to move against stop288 and spring 284 to be possibly compressed, depending on the degree ofrotation of cam 272. Because of this the effective orifice size oforifize 254 is substantially increased thereby enabling a greater rateof fuel flow to occur therethrough and because of the increasedeffective flow area of orifice 254, the magnitude of pressure P₆ isincreased resulting in an increased rate of fuel flow through thevaiable restriction means 201 and 203 of assembly 194.

Because of the increased rate of fuel flow to the engine 12, the enginespeed starts to increase causing an increase in the speed signal, N, aswell as an increase in P_(t1).

During such engine acceleration, governor valve 246 (FIG. 1) will beheld open while the pressure differential of P₄ - P₇ will be maintainedand modulated by the metering regulator assembly 142 as previouslydescribed. Because of such increasing engine speed, speed sense meanswill increase the magnitude of not only P₅ but alos P₄ so as to have thedifferential therebetween increase in an exponential relationship toincrease in speed. Generally such increases will continue until thevalue of P₅ within governor chamber 250 is sufficient to overcome thecombined resistance of the force of spring 284 and pressure P₄ (themagnitude of which is influenced by the downstream engine pressure,governor valve 246 and assembly 194) so as to return governor valve 246to the right to its then proper position to maintain the required fuelflow. Upon this occurring, the value of P₄ has increased sufficiently toagain place valve member 174 of pressure head regulator 142 (FIG. 2)into the steady state modulating mode of operation.

From the preceding it should be apparent that: (1) as speed N eitherincreases or decreases the relative values of P₅ and P₄ will be effectedcausing the governor valve 246 to respond accordingly as well as havingthe modulating valve 174 bypass more or less fuel; (2) as burner inlettemperature increases or decreases the effective flow area of variablerestriction means 201 and 203 decreases or increases therebycorrespondingly permitting an increase or decrease in the rate ofmetered fuel flow; and (3) as compressor discharge pressure increases,the value of P_(t4) will generally increase thereby further restrictingor preventing, in accordance with a schedule determined generally by theconstants of the system, the degree of fuel being bypassed by modulatingvalve 174.

In order to ahcieve engine deceleration, shaft 270 is rotated generallycounter-clockwise thereby permitting spring seat 282 to move lever end280 to the right with pressure P₅ in chamber 250 then being able to movegovernor valve 246 to a position relatively close to orifice 254 asdetermined, for example, by the idle abutment 290 if cam 272 issufficiently rotated to a position corresponding to a condition of idleengine operation.

As can be seen, static inlet air pressure P_(s) is directed from sensingmeans 488 of engine 12 to chamber 466 (FIG. 2) via conduit means 490.The value of P_(s), because of the location of sensing means 414 aswithin a venturi-like inlet of the engine, may actually be of amagnitude less than ambient static air pressure and to that extent maybe considered as a partial vacuum. In comparison, the total inlet airpressure P_(o) (which is preferably derived at a point in the ambientair which, for practical purposes may be considered being static air) isdirected from sensing means 486 of engine 12 to chamber 464 (FIG. 2) viaconduit means 484 so as to thereby create a pressure differential ofP_(o) - P_(s) across diaphragm 458 which may be considered as a signalor indicia of weight rate or mass rate of air flow to the engine 12. Theresulting force on diaphragm 458 is, of course, one urging the diaphragmdownwardly. The resulting force created across diaphragm 458 istherefore a signal indicative of the actual rate of air flow to theengine 12. One of the problems, however, is that the P_(o) and P_(s)pressures are of a relatively low magnitude and often not directlyemployable for other control functions.

Therefore, chamber 468 has a hydraulic pressure P_(h2) applied theretowhich is the result of communication through conduit means 482,restriction means 530, and conduit means 528 which communicates withconduit means 520 being supplied with a relatively high regulatedpressure P_(h1) from pump means 522. As a consequence thereof, diaphragm462 has a pressure differential thereacross of P_(h2) - P_(s) while, aspreviously described diaphragm 458 has a pressure differential ofP_(o) - P_(s) applied thereto. Further, it can be seen that asdiaphragms 462 and 458 move upwardly valving member 472 will to somedegree further open the communication as between chamber 468 and passage476 leading to the low pressure, P_(h3), return conduit 478. Suchopening movement of valve member 468 permits an increased rate of returnflow and this coupled with the restrictive effect of restriction means530 causes a reduction in the magnitude of pressure P_(h2) so as to makeit more nearly approach the lower absolute limit of pressure P_(h3).Consequently, since the total actual movement of valving member 472 maybe very small while the variation on the magnitude of pressure P_(h2)may be substantial, assembly 352 may be considered as a high gainpressure balance apparatus functioning as an air flow transducer. Thevariation in the magnitude of pressure P_(h2), as should be apparent,may then be considered as a signal indicative of one of the engineoperating parameters, namely, the rate of air flow to the engine.

Generally, if a graph were plotted of P_(h2) - P_(s) against P_(o) -P_(s), the resulting locus of points would define a straight line withthe slope thereof being determined by the respective areas of diaphragms458 and 462 while the intercepts of such resulting plotted line would bedetermined by the original settings of the components thereof.

Another engine operating parameter, compressor discharge pressure (CDP)and designated as P_(t1), is sensed as at 226 of the engine 12 andapplied first, via conduit means 374, to chamber-like areas 362 and 364of assembly 344 from where, as by conduit means 448, it is applied topassage 428 of assembly 350. As shown, pressure P_(h2), of chamber 468of the transducer 352, is also applied via conduit means 450 to chamber418 on one side of diaphragm 414 while a second variable pressure P_(t3)is applied to chamber 416 on the other side of diaphragm 414 as byconduit means 422 thereby creating thereacross a pressure differentialof P_(h2) - P_(t3). The derivation of pressure P_(h2) has already beenexplained; however, pressure P_(t3) is obtained by the coaction of tworestriction means generally down stream of the inlet 372 of assembly344.

That is, compressor discharge pressure P_(t1) flows from conduit means384 to conduit means 402 via orifice 400 which is variably restricted byvalve portion 396 of valving member 394. The degree to which the flowthrough orifice 400 is restricted is primarily dependent upon theposition of valving member 394 which, in turn, is determined by thepressure differential across diaphragm 376 created by pressure P_(t1) inchamber 378 and ambient atmospheric pressure in chamber 380. Therefore,generally, the greater the magnitude of P_(t1) or the lesser the ambientatmospheric pressure, the more diaphragm 376 will tend to move to theright and the greater the restrictive effect to flow through orificemeans 400 with, of course, the greater drop in pressure thereacrossresulting in a further reduction in the magnitude of pressure P_(t2).

At this point it should be brought out that pressure P_(t2) iscommunicated, via conduit means 534, to chamber 498 (of the transmissioncontrol valve assembly 342) on one side of diaphragm 496 on the otherside of which chamber 500 is exposed to the hydraulic pressure P_(h2)thereby resulting in a pressure differential of P_(t2) - P_(h2) acrossdiaphragm 496.

Referring again to assembly 344, it can be seen that a secondrestriction 404 causes the pressure P_(t2) to again drop to some valueP_(t3) in conduit means 420. The magnitude of P_(t3) will, of course, bedependent on, and nearly a percentage (as for example 90%) of, themagnitude of pressure P_(t2) as well as the rate of flow in conduitmeans 420. In any event, the pressure P_(t3) thusly derived istransmitted via conduit means 422 to chamber 416 of assembly 350.

It should also be pointed out that since one of the factors determiningthe magnitude of pressure P_(t3) is its rate of flow in conduit means420, that safety solenoid valving assembly 584, ambient temperaturesensing assembly 552 (FIG. 1), priority valve assembly 538 (FIG. 1) aswell as exhaust pressure of atmosphere ATM, contribute to thedetermination of such flow. That is, the more valve 570 (of temperaturesensing assembly 552) is opened due to a decrease in sensed ambienttemperature, the more priority valve member 546 is opened due to thecontrol exercised thereover by associated linkage means, and the openingof the orifice 596 is solenoid valve means 584 will all contribute tothe rate of flow of P_(t3) to ambient atmosphere and therefore serve toreduce the magnitude of pressure P_(t3).

In view of the preceding it can be seen that valving member 394functions as a means for more accurately tailoring or modifying thevalue of a control pressure P_(t2) to the requirements of the particularassociated engine 12. As should be apparent, the value of magnitude ofP_(t2) is generally a function of P_(t1) and, in the embodimentdisclosed, the value of P_(t2) is generally permitted to incrementallyincrease a lesser amount than corresponding incremental increases inP_(t1). However, depending upon the particular engine characteristics,it would be just as possible to have valving member 394 provide thereverse effect during its normal operating range.

In any event, with reference to the transmission control valvingassembly 342, when the value of P_(t2) in chamber 466 becomescomparatively sufficiently low, valve member 506 will move upwardlythereby permitting pressure P_(h1) to be communicated to conduit means340 leading to the transmission control means 338 of FIG. 3 and in sodoing cause the speed ratio as between the input shaft 334 and outputshaft 336 to change in order to effectively vary the torque therebetweenso as to have the output shaft 634 of engine 12 sense an increase intorque load applied thereto. This will result in the speed of the enginetending to decrease; however, the speed change is sensed as by speedsensor 70 with the resulting effect that additional metered fuel flow isprovided in order to maintain the selected speed setting and enginetemperature.

Referring to assembly 350, it can be seen that the magnitude of pressureP_(t4) is dependent upon the magnitude of pressure P_(t1) and therestrictive effect of the variably positionable valve portion 426 ofvalving member 424. Generally, when the magnitude of the differentialbetween pressures P_(t3) and P_(h2) becomes such as to move valvingmember 424 upwardly, pressure P_(t1) is permitted to flow from passage428 through chamber 430 and into conduit means 186 and, in the processcreate a lesser pressure of P_(t4) within conduit means 186 and chamber160 of the metering head pressure regulator assembly 142. Generally, thegreater the magnitude of pressure P_(t4) the greater will diaphragm 156of assembly 142 tend to close valving member 170 and thereby reduce theamount of fuel flow permitted to be bypassed from conduit 120 to conduitmeans 140 and 138.

Now considering certain modes of engine operation, the invention asherein disclosed provided means for enabling a limited fuel flow to theengine upon initiation of the engine start sequence but prior to actualengine cranking, which, of course, would mean zero engine speed. Thatis, upon initiation of the start sequence, the boost pump means suppliesfuel which, by throttling valve 41, is regulated to a relatively lowpressure P₂ (as for example, 7.0 psi.) within chamber 46 (FIG. 3) fromwhere such fuel passes through the related fluid circuitry until itreaches chamber 192 of assembly 194 from where it must pass throughcalibrated passage 213 of member 211. During a very short period of flowof such zero-engine-speed fuel, the igniter within the engine causesignition and the engine starter means is actuated to cause enginecranking during which pumping means 52 (FIG. 3) starts to provideincreasing fuel flow to the engine with the regulation of such flowbeing achieved by the pressure head regulating assembly 142 (FIG. 2)including the bypass valve 170 which receives its back pressure P₇ byvirtue of member 211 in assembly 194 (FIG. 1).

During conditions of engine acceleration the various components coactgenerally as follows. The throttle control 302 is rotated causing levers292 and 313 and shaft 270 to rotate generally clockwise causing cam 272to, through lever 274, move governor valve 246 to its fully openedposition against stop 288 thereby permitting an increase in fuel flow tothe engine. Such increase in fuel flow causes an increase in enginetemperature which is reflected as an increase in CDP pressure P_(t1) aswell as increases in pressures P_(t2), P_(t3) and P_(t4). In valveassembly 350, (FIG. 2) immediately prior to the initiation of engineacceleration, as during steady state operation, valve member 424 was inits upper-most position against stop 444 thereby presenting the leastpossible restriction to flow from passage 428 to chamber 430. Therefore,as CDP pressure P_(t1) increases upon initiation of the accelerationmode, the increased magnitude of P_(t3) against diaphragm 414 will movevalve member 424 somewhat downwardly to thereby modulate the resultingmagnitude of P_(t4) which, via conduit means 186, is transmitted tochamber 160 of the pressure head regulator assembly 142. The increased,but modulated, pressure P_(t4) thusly applied to diaphragm 156 resultsin an increased force tending to move the bypass valve member 170 towarda more nearly closed position thereby reducing the rate of flow of fuelbeing bypassed back to low pressure via conduits 140 and 138. That is,even though the function of assemgly 142 is to modulate bypass fuelduring all conditions of engine operation, it, nevertheless, bypasses alesser rate during conditions of engine acceleration. According, duringthe time that the engine is undergoing acceleration, the rate of fuelflow, across the effective flow areas of the fully opened governor valve246 and the burner inlet temperature sensing assembly 194, is controlledby the position of bypass valve 170 which, in turn, is being determinedby the modulated pressure P_(t4) and CDP pressure P_(t1). Since pressureP_(t1) is a function of the temperature of the burner which, in turn, isa function of the rate of fuel flow, it becomes apparent that theabove-described components are functioning in a closed loop manner sothat only that precise rate of fuel flow will be permitted as willprovide the desired optimum engine operating temperature. Moreover,should the safe operating limits of the engine, that is surge orover-temperature, be approached as determined by the relationship ofP_(t3) to airflow the diaphragm 414 will move downwardly causing thevalve 426 to further restrict orifice 428 and reduce P_(t4) to maintainengine operation within safe limits. This is the primary closed loopeffect.

It should also be pointed out that at initiation of the accelerationmode, pressure P_(t2) also increased and such, communicated via conduitmeans 534 to chamber 498 of the transmission control valve assembly 342,causes the valve member 506 to momentarily move downwardly to reduce theload on the engine 12 thereby enabling the engine to start to increasein speed more quickly. After the momentary unloading of the engine 12,the increased air flow results in a pressure differential of P_(o) -P_(s) (amplified as previously described) which increases in magnitudecausing hydraulic pressure P_(h2) in chamber 500, of transmission valveassembly 342, to increase and return valve member 506 to its modulatingcondition, depending on the value P_(t2) which also increases as theengine increases speed.

The above described acceleration mode continues until the speed sense 70develops a sufficient pressure differential of P₅ - P₄ to cause governorvalve 246 to again move to the right and again contribute to the overallfuel metering function. Because of this, generally, no furtheracceleration fuel flow occurs; however, regulator assembly 142 stillcontinues to modulate and, since the magnitude of pressure P₄ in chamber152 at thist time is greater than at initiation of acceleration, agreater force is experienced tending to move bypass valve 170 to theright with the result that a greater rate of fuel flow can be bypassedto low pressure return while maintaining the desired pressure drop ofP₄ - P₇ during such resulting steady state operation. At such resultingsteady state, as previously generally indicated, the magnitude ofhydraulic pressure P_(h2) has sufficiently increased to overcome thepreviously increasing force developed by the previously increasing valueof P_(t3) and consequently move valve member 424, of assembly 350,upwardly against its stop 444.

During deceleration the reverse is generally true in that because of theclosure of governor valve 246 to its then minimum flow, the rate of fuelflow therepast is drastically diminished resulting in a decrease inburner temperature and CDP pressure P_(t1). As a consequence thereof,resulting pressures P_(t2), P_(t3) and P_(t4) are reduced. The reductionin pressure P_(t4) sensed in regulator assembly 142 enables bypass valve170 to be moved toward its maximum position so as to bypass a greateramount of fuel back to conduit means 140 and 138; the reduction inpressure P_(t3) serves to assure maximum communication as betweenpassage 428 and chamber 430 of valving assembly 350; as engine speeddecreases during deceleration P_(t1) will further decrease resulting ina reduction in pressure P_(t4) which, in turn, results via the action ofthe bypass valve in a reduction in fuel flow delivered to the engine;while the reduction in pressure P_(t2) sensed in chamber 498 of assembly342 causes valve member 506 to move upwardly thereby loading the engineso as to have the engine function as a braking force during vehiculardeceleration.

Now, let it be assumed that the engine is operating at idle conditionand power lever 302 is as shown. In this idle position the minimumengine speed is essentially controlled by the idle stop 290 which limitsthe lever 276 from following the cam 272. At this time the enginetemperature may be set or determined by the position of the priorityvalve 312 which is determined by lever 318 coacting with cam surface 322of lever-like cam member 293. Generally, in adjusting such enginetempeature, if more temperature is desired screw 320 is adjustedupwardly relative to lever 318 so as to result in a greater bleedthrough orifice 548 thereby reducing the magnitude of pressure P_(t3).

As the power lever 302 is slowly rotated from its idle position throughapproximately its first ten percent (10%) of total travel, enginetemperature and power are gradually increased by gradually opening thepriority valve means 312 as dictated by the controlling cam surfaces 321and 322. Such opening of the priority valve reduces the magnitude ofP_(t3) and P_(t2) momentarily causing the transmission actuator valve506 to move upwardly and admit higher hydraulic pressure to thetransmission control means 338. This, in turn, causes the torqueconverter stator angle of the transmission 332 to be changed to a lowertorque multiplication thereby placing an extra load on the engine.Because of this increased load, the engine speed may tend to decrease;however, such tendency is overcome by the governor valve 246 providingan increase in the rate of fuel flow to the engine which, of course,results in a higher engine temperature, CDP pressure P_(t1) and enginepower output. When the power lever or throttle lever 302 reaches about10 percent of its maximum travel, the engine burner temperature has beenbrought to the normal maximum allowable operating temperature which, forexample, may be in the order of 2,200.0°F. Further throttle advance, inthe preferred embodiment, will increase engine speed but not burnertemperature.

That is, as the control pedal or lever 302 is rotated from itsapproximately 10 percent to its approximately 90 percent of its maximumtravel, the then position of priority valve 312 is not changed becauseduring such range the contour of cam surfaces 321, 322 would be of aconstant radius. (Such contour, of course, could be any suitable contourcompatible with the related engine.) This would maintain engine burnertemperature at a constant value while engine speed would increase due tocam 272 placing a greater spring preload force into spring 284 of thegovernor valve assembly 240 as previously described.

During the last 10 percent of maximum movement of power lever means 302,lever 313 will enentually have portion 329 thereof abut against fixedstop 328. At this time, engine speed has reached a maximum speed imposedby such stop 328. However, further throttle advance after lever 313 isbrought into such abutting engagement, causes lever 292 to move, againstthe spring 314, relative to lever 313 with the limit of such relativemovement being determined as by the length of slot 310. During suchperiod of relative movement between levers 292 and 313 the contour ofcam surface 321 is such as to cause priority valve 312 to open to afurther extent thereby again reducing the value of P_(t3) and P_(t2) andcausing the transmission valve 506 to move upwardly to reduce the torqueratio through the transmission assembly 332 and thereby again place anadditional load on the engine with the result that, as before,additional fuel is metered to the engine causing an increase in burnertemperature and engine output power. This last ten percent of movementcan be generally correlated to what is commonly referred to as a"passing mode" function in the prior art.

In view of the preceding, it can be seen generally that as the value ofP_(t3) and P_(t2) is made to increase or decrease the transmissionselector valve 506 is moved downwardly or upwardly, respectively, inorder to thereby correspondingly decrease or increase the torquemultiplication through the transmission assembly 332 and, in such way,by increasing or decreasing the load on the engine, maintain thetemperature of the engine burner 214 at a selected optimum temperature.

The preceding is generally depicted by the graph of FIG. 4 wherein thevalue of compressor discharge pressure (CDP) divided by the staticambient pressure, P_(s)(amb.), is plotted against the mass rate of airflow Wa .√T (wherein T is the ambient air temperature at the engineinlet) divided by the same value of static ambient pressure,P_(s)(amb.). Line 660 depicts, generally, a nominal steady state curvewhich may represent a burner temperature of, for example, 1,900°F. Line662 depicts a nominal acceleration or increased power curve which, forpurposes of illustration may represent a burner temperature of 2,200°F.,while curves 559 and 661 respectively indicate fragmentary portions ofcurves obtained during the "passing mode" previously described.

Lines 663, 664, 665 and 666 are merely illustrative of characteristicgovernor hooks or curves determined generally by the action of thegovernor valve 246. If it is assumed that hooks 663 and 664 respectivelydepict 50 percent engine speed and 60 percent engine speed, it can beseen that with the engine operating at point 667 of the steady statecurve and acceleration to some point 668 is desired, by rotation of thepower lever 302 burner temperature will increase from point 667 to point669 and thereafter remain at the substantially constant temperature ofthe acceleration curve 662 until the governor valve 246 again reducesfuel flow, in accordance with governor hook curve 664 and burnertemperature decreases until point 668 is attained at the comparativelyreduced temperature of the steady state curve 660.

The curves illustrated by portions 559 and 661 depict the resultingincrease in burner temperature and air flow resulting from the throttlelever 302 being moved through the last 10 percent of its maximum travelas previously described.

It should be pointed out that if, for example, 50 percent engine speedis considered to be idle engine operation that under idle conditions theengine may actually be developing excess power which would normally tendto put the associated vehicle in motion. Therefore, the invention asherein disclosed, provides means for arbitrarily, at idle engineoperation, lowering the burner temperature while maintaining enginespeed thereby effectively reducing the engine power output. This isaccomplished by the priority valve 312 being urged most nearly closed atconditions, indicated by the throttle linkage, to be idle engineoperation. The result of this is that pressure P_(t3) and P_(t2)increases, comparatively, and more nearly approaches the value of P_(t1)thereby causing the transmission selector or control valve 506 to movedownwardly in order to threby reduce the load on the engine 12. As thishappens, the engine's tendency to increase in speed is offset by thebypass valve 170 and governor valve 246 responding in a manner causingan appropriate reduction in fuel flow to the engine with, of course, anattendant reduction in burner temperature. Consequently, instead of theengine operating at the temperature of point 667 of FIG. 4 during idle,it will operate at some selected lower temperature indicated at 670.

With reference to FIG. 1, two other means, namely the compressor inlettemperature sensor assembly 552 and the temperature control solenoidassembly 584 (FIG. 2) provide functions somewhat similar to the priorityvalve 312 with the exception that the solenoid valve assembly 584 ispreferably of the "on - off" type whereby it is responsive to apredetermined engine over-temperature condition and upon sensing suchcondition causes valve orifice 596 to be closed by valve 592. When thishappens, all of the curves, 660, 662, 661, and 559 of FIG. 4 are shiftedto respective lower temperatures until the over-temperature condition iscorrected. In contrast, valve assembly 570 is of the variable bleedtype. However, it too, in response to sensed increase in compressorinlet temperature more nearly closes off the bleed of P_(t3) toatmosphere thereby again increasing the value of P_(t3) and P_(t2) andcausing a reduction in fuel flow in the manner previously described viatransmission control valve 506.

Further, with reference to assemblies 344 and 350, it can be seen thatduring steady state operation valving portion 426 of valve member 424can be considered as permitting substantially free flow through conduitmeans 186 applying unmodulated P_(t4) to chamber 160 of metering headassembly 142 (FIG. 2). Consequently, during such periods of operation,the variations in CDP pressure p_(t1) are reflected in values of P_(t4)which is employed to cause bypass valve 170 to be modulated and therebycontinually monitor; indirectly, the engine temperature via the agencyof CDP pressure P_(t1).

The speed switch assembly 602 of FIG. 1 is employed in combination withthe engine start sequence logic means 600 of FIG. 3 which is shown ingreater schematic detail in FIG. 7.

In FIG. 7, the logic means is illustrated as comprising a plurality ofAND gates 800, 802, 804 and 806; OR gates 808 and 810; electricallatching means 812 and 814; timing means 816, 818 and 820; turbine inlettemperature sensitive signal producing means 822 and thermocouple 824which may be within generally the turbine section of the engine 12;temperature reference means 826 and 828; comparators 830 and 832; signalproducing means 834 and 836 indicative of particular selected ranges ofengine speed; an inverter 838; and related associated vehicularcircuitry 840.

At the right side of the logic network are, schematically illustrated,solenoid valve assembly 584 (shown also in FIG. 2); vehicular accessorymeans 842 such as, for example, air conditioner means driven by theengine 12; master fuel shut-off valving means 844 as may be situatedwithin conduit means 652 of FIG. 1 leading to the engine 12; and enginestarter motor solenoid means 846 for cranking the engine during startingoperations.

Under normal conditions, the starting sequence would be as follows. Whenthe manual ignition switch is moved to the "on" position the accessorymeans 842 will be energized; however, in order to initiate a start, thefollowing conditions must be satisfied. That is, switch 850, indicativeof transmission 332 selector lever position, must be in "park" andengine speed, as sensed by switch 602, must be less than 10 percent ofmaximum speed. Signal producing means 834 is responsive to such enginespeeds less than 10 percent.

Start is then initiated by a momentary deflection of the ignition switch848 to the "start" position. At such start initation the followingconditions occur: (a) time delay means 818 functions to de-energize theaccessory means 842 for, for example, 20.0 seconds so as to remove anysuch load from the engine; (b) starter motor means 846 is energizedcausing starter engagement with the engine 12; (c) the master fuel relayor valving means 844 is energized thereby switching on the flow of fuel;and the safety solenoid valving means 584 is energized opening port 596(FIG. 2) and thereby setting the nominal control acceleration and steadystate operating lines or curves to the normal mode of operation. Thecombustion chamber temperature is compared to a minimum allowablereference at, for example, 3.0 seconds after start initiation in orderto see if ignition had occurred. Such time delay is achieved by timedelay means 820 while the temperature sensed by probe 824 is comparedagainst the minimum temperature reference means 826.

With the above normal conditions and when engine speed reaches, forexample, 45 percent of its maximum speed, (as sensed by switch means 602and indicated by engine speed signal means 836 with comparable means 834now being switched to its other mode) the starter means 846 isde-energized and the following normal run conditions are established:(a) the solenoid valve means 584 is "on;" (b) the master fuel relay orvalve means 844 is "on;" (c) the starter motor means (which, of course,comprises its associated relay means) 846 is "off;" and the vehicleaccessory means (which, of course, also comprises its associated relaymeans) 842 is "on".

However, the above described normal start sequence will be aborted ifany of the following conditions should occur. If after supplying fuel tothe combustion chamber of the engine 12, for example, for 3.0 secondsthere is absence of or lack of sufficient ignition, the start sequenceis aborted. The 3.0 seconds delay is achieved by time delay means 820and a minimum temperature of, for example, 1,400°F. is employed as areference to indicate that proper "lite-off" of the combustion chamberhas occurred. The temperature of the combustor is sensed, of course, byprobe 824 and compared to the minimum temperature reference of means826, as at 1,400°F., to indicate whether the minimum prescribedtemperature has been attained. If the combustor temperature is belowminimum limits comparator 830 then, through the action of AND gate 806and OR gate 808 applies a signal to the "reset-off" terminal 852 oflatch means 812 shutting-off the master fuel relay means 844 and, at thesame time, through AND gate 806, OR gate 808 and OR gate 810 applies asignal to the "reset-off" terminal 854 or latch means 814 de-energizingstarter means 846.

If overcrank has occurred, that is, engine speed has not reached theassumed selected speed of 45 percent of its maximum speed within, forexample, 20.0 seconds of start initiation, the start sequence is againaborted. The time delay is accomplished by time delay means 818. Sinceat this condition engine speed range signal producing means 836 isproviding an output signal which is compatible with the output signal oftime delay means 818, such time delay signal through AND gate 802 and ORgates 808 and 810 will be applied to the "reset-off" terminals 852 and854 of latch means 812 and 814 thereby de-energizing the master fuelrelay 844 and starter motor means 846.

If an over-temperature condition occurrs before the engine speed hasreached the assumed 45 percent of its maximum speed the start sequencewill be aborted. For purposes of illustration, it is assumed that asensed temperature in excess of 2,000°F. indicates suchover-temperature. At this time the temperature is, of course, sensed byprobe 824 and compared against the temperature reference means 828 whichestablishes the assumed 2,000°F. The signal produced by the comparatormeans 832 is compatible with the signal being produced by speed signalproducing means 836 and therefore through AND gate 806 and OR gates 808and 810 a signal is applied to the "reset-off" terminals 852 and 854 oflatching means 812 and 814 with the resulting de-energization of means844 and 846 as previously described.

If "lite-off" actually occurs but is followed by a "flame-out" therebyreducing the combustor temperature to, for example, 1,200°F. or less andthis low temperature exists while the engine speed is less than theassumed 45 percent and at an assumed time of 3.0 seconds after startinitiation, the start sequence will again be aborted. This condition isagain established by the time delay means 820 and temperature referencemeans 826 providing an output to the comparator means 830 which alsoreceives a temperature signal from probe 824. Similarly to the "nolite-off" condition previously described, the comparator 830 through theagency of AND gate 806 and OR gates 808 and 810 again applies a signalto the "reset-off" terminals 852 and 854 of latch means 812 and 814 withthe same result as previously described.

Obviously, the start sequence is also aborted should the ignition switch848 be moved to the "off" position.

As part of the safety included within the overall turbine controlsystem, solenoid valve assembly 584 (see also FIG. 2) is energized to anopen condition at start initiation thereby establishing the nominalacceleration and steady state operating lines or curves to the normalmode of operation. However, if an over-temperature condition shouldexist (sensed by probe 824 and compares to temperature reference means832) for a time span of, for example, 3.0 seconds, as determined by timedelay means 816, the signal from the time delay means will causede-energization of solenoid valve means 584 resulting in closure oforifice 596 (FIG. 2) and the consequent lowering of the nominalacceleration and steady state operating lines or curves (reduction ofrate fuel flow). Although the solenoid assembly 584, once de-energized,will not cause an abort condition, it will inhibit a re-start.

In order to reset the solenoid valve assembly 584 and re-initiate thestart sequence, the entire system must be manually reset which isaccomplished by returning the ignition switch 848 to its "off" position.

In view of the preceding, it can be seen that the invention, in at leastone of its aspects, provides a turbine engine control system whichautomatically monitors certain parameters during engine starting toassure the attainment of only normal accepted conditions whileautomatically aborting engine starting should certain establishedparameters not be met.

During normal operation, the system functions in a generally closed loopfashion to maintain selected optimum engine operating temperatures asby, when necessary, increasing or decreasing the load sensed by theengine while still providing for increased or decreased fuel flows, ifnecessary, to provide for increased or decreased engine speeds.

For example, referring to the graph of FIG. 5 the maximum anddeceleration fuel limits are illustrated at 900 and 902 (such beingdetermined by plotting fuel flow to the engine against CDP pressureP_(t1)). Such limits may be considered as being those which the overallfuel control system 10 is capable of delivering were it not for theoverrriding limiting and monitoring effect of the other componentsoperating in closed loop control.

Such interrelationship is illustrated graphically (in somewhatexaggerated form) in FIG. 6 wherein the fuel flow is plotted againstengine speed, N. In FIG. 6, the absolute maximum fuel limit curve 900'corresponds to curve 900 of FIG. 5 while the minimum deceleration curve902' corresponds to curve 902 of FIG. 5. Also, depicted by the generallyshaded portion 904, is the region where the system is operating as aclosed loop control so as to in fact establish a lower maximum fuellimit, as depicted by curve 906.

In view of the preceding, the invention provides a turbine controlsystem which has certain portions thereof operating, during certainoperating conditions, in a scheduling mode of operation while at otherconditions of operation other interrelated portions operate in a closedloop mode as to closely meter the fuel flow to the engine in order toeither maintain a selected desired optimum engine operating temperatureor to insure surge free operation for such conditions. To this end, itshould also be brought out that during steady state operation, ifadditional power is required to maintain steady state operation, such isinitiated by the movement of the throttle control or power lever 302 andsuch movement can be considered as a part in the overall feed-back forachieving closed loop operation.

In addition to the preceding, it can be seen that assembly 344 (FIG. 2)along with its related components provides a fail-safe structure. Thatis, generally, as the value of P_(t2) should decrease, some relatedmeans downstream thereof react in a way requiring an increase in fuelflow. If the screen 360, which is provided to prevent foreign matterfrom entering the system, should start to become clogged, a substantialpressure drop could occur thereacross with the result that P_(t2) wouldbecome an inaccurate signal causing increased fuel flow when in fact nosuch increased fuel flow would be required. Therefore the provision ofvalve means 366 operated by the deflection of the screen 360 (suchdeflection occurring in response to the un-wanted pressure differentialthereacross) opens conduit means 370 and effectively applies the higherpressure (or some significant portion thereof) within the chamber-area362 to the same means downstream of pressure P_(t2) which, in turn,causes such means to reduce fuel flow instead of increasing it. Theengine is thereby protected against over-temperature operation and thevehicle operator, upon noticing, over a period of time, a reduction inthe power output of the engine will have the system checked. In view ofthis, it can be seen that such a valving arrangement becomes significantanywhere a filter means is required through which flows an actuatingfluid with such fluid being employed to develop an actuating pressure toa related device downstream thereof.

Also, the compressor inlet temperature sensing means 552 is quite uniquein that it automatically functions to alter the rate of fuel flow to theengine depending on the ambient compressor inlet temperature. Sinceturbine engines are sensitive to inlet temperature the provision ofmeans 552 enables the entire fuel control system to continue operationgenerally independently of ambient temperature while means 552 providesan overriding effect to either increase or decrease the metering rate inaccordance with variations, in ambient temperature. As can be seen,generally, CDP pressure is directed to first restriction means definedas by, for example, means 344, which in turn, applies an output signalto the remaining fuel control means for determining the required rate offuel flow. From such first restriction means, part of the output signalis bled away by the action of the temperature sensitive means 552 andthe degree of such bleed in turn effects the ultimate magnitude of suchoutput signal.

Although the invention has been disclosed employing a transmissionassembly 332 the invention is not so limited in that other meanssuitable for varying the load of the engine may be employed. Forexample, suitable braking or clutching means may be employed as, forexample, interconnecting the compressor and power turbine, or othermeans such as variably positionable turbine nozzle means may beemployed. Any of such means may be employed. Any of such means would beoperatively connected to suitable servo means such as valving assembly342 in order to achieve engine loading and unloading consistent with thedisclosure made herein.

Although only one preferred embodiment of the invention has beendisclosed and described, it is apparent that other embodiments andmodifications of the invention are possible within the scope of theappended claims.

I claim:
 1. Fail safe apparatus, comprising house means, chamber meansdefined at least partly by said housing means, inlet means for admittinga relatively high pressure fluid into said chamber means, first outletmeans including a first restriction for directing said fluid from saidchamber means to associated means to be acted upon by said fluid inaccordance with the magnitude of said pressure of said fluid, filtermeans situated generally in the path of flow of said fluid, secondoutlet means having a lesser restriction than said first restriction ofsaid first outlet means for at times dircting said fluid from saidchamber means to the associated means, and valving means for controllingthe communication between said second outlet means and said chambermeans, said valving means being operatively controlled by the deflectionexperienced by said filter means due to a pressure differential acrosssaid filter means generated by said fluid flowing through said filtermeans and an increasing restrictive effect to flow through said filtermeans created by clogging of said filter means by particles of dirt,whereby clogging of said filter in the absence of said valve wouldproduce an undetectable, lower-than-normal pressure having an undesiredeffect on the associated means, as compared to said filter not beingclogged, but whereby, upon said filter becoming clogged sufficiently tocause said valve to open, a higher-than-normal pressure is produced andsaid second outlet means, said higher-than-normal pressure beingdetectable and useable to have a desired effect on the associated means.2. Fail safe apparatus according to claim 1 wherein said filter means issitutated within said chamber means so as to define a generally movablewall-like structure wih first and second chamber-like portions onresponsive sides thereof.
 3. Fail safe apparatus according to claim 1and further comprising resilient means for resiliently resisting saiddeflection of said filter means.
 4. Fail safe apparatus according toclaim 1 wherein said filter means is situated within said chamber meansso as to define a generally movable wall-like structure with first andsecond chamber-like portions on respective sides thereof, and furthercomprising resilient means for resiliently resisting said deflection ofsaid filter means, said resilient means being situated within one ofsaid chamber-like portions and operatively connected to said filtermeans.
 5. Fail safe apparatus according to claim 1 wherein said inletmeans communicates with said chamber means upstream of said filtermeans, wherein said first outlet means communicates with said chambermeans downstream of said filter means, and wherein said second outletmeans communicates with said chamber means upstream of said filtermeans.
 6. Fail safe apparatus according to claim 1 wherein said chambermeans comprises passage means for the flow therethrough of said fluid.7. Fail safe apparatus according to claim 6 wherein said filter meanscomprises a relatively flexible wall-like member with a plurality offlow-through passages formed therethrough, said flexible wall-likemember being peripherally anchored within said passage means, whereinsaid flexible wall-like member defines at opposite sides thereof firstand second chamber-like portions, wherein said second outlet means isadapted for communication with said first chamber-like portion, andwherein said valving means is carried by said flexible wall-like memberfor permitting varying degrees of communication between said firstchamber-like portion and said second outlet means in accordance with thedegree of deflection of said flexible wall-like member.
 8. Fail safeapparatus according to claim 7 and further comprising spring meansoperatively connected to said flesible wall-like member for normallyurging said wall-like member and said valving means in a direction atleast tending to terminate communication between said first chamber-likeportion and said second outlet means.